Conducción hopping en películas nanocristalinas del compuesto CZTSe usado como capa absorbente en celdas solares

Abstract

Here, we present electronic and transport properties of quaternary Cu2ZnSnSe4 (CZTSe) nanocrystalline films fabricated by physical co-evaporation. The samples were grown on soda-lime glass substrates and synthesis parameter ranges, Cu mass and substrate temperature were varied. Using thermopower at room temperature and spectral transmittance we found that the material is characterized by n-type conductivity and forbidden energy bandwidth of 1.7 eV, respectively. Electrical conductivity means (low temperature region; 90-200 K) showed that conductivity processes occur via variable range hopping between extended states. We obtained the parameters characterizing this mechanism, activation energy (Whopp), and range hopping (Rhopp), by employing the percolation theory and diffusion model. The density of defect states near the Fermi level of the material, N (EF) of the CZTSe samples is about 3,403x10 18 cm -3 eV -1 . We found a correlation between deposition parameters and electrical properties and observed a parameter influence on the formation of additional phases in the compound.

Mathematical Models to Determine the Conductivity of a Cztis Photovoltaic Material as a Function of the Synthesis Temperature

“…The information in the table shows the different parameters obtained by AFM, observing that the roughness averages and all the parameters for each sample tend to decrease slightly as the synthesis temperature is increased, with which it could be inferred that the higher the temperature, a lower roughness is obtained and the conductivity of the CZTiS material is better. The impedance information is obtained from the corresponding Nyquist diagrams made for each sample in solid state Table II; since these diagrams represent a transfer function and in them the electrical behavior can be evidenced through the resistance and reactance identified in the real and imaginary part of said diagrams; the magnitudes of their conductivity can also be determined, and in this way they can be classified as semiconductor materials (18). For this, a system was used by coupling a reference resistance to a breadboard and connected to the impedance equipment.…”